Devices and methods for the restoration of a spinal disc

ABSTRACT

A system and method is provided for maintaining a proper intervertebral disc height during the replacement or augmentation of the spinal disc. In one embodiment, a cannulated distractor is used to distract the adjacent vertebrae and maintain a proper disc space height. The cannulated distractor is fluidly connected to a source of fluent material for injection into the disc space. The distraction includes a distraction tip resident within the disc space that includes a central lumen and a number of openings communicating with the lumen to dispense the fluent material within the disc space.

REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to provisional applicationSerial No. 60/336,002, entitled “Devices, Methods and Assemblies forIntervertebral Disc Repair and Regeneration”, and provisionalapplication Serial No. 60/336,332, entitled “Pretreatment ofCartilaginous Endplates Prior to Treatment of the Intervertebral Discwith an Injectable Biomaterial”, both of which were filed on Nov. 1,2001, and the disclosure of which are both incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] The present invention relates generally to the treatment ofspinal diseases and injuries, and more specifically to the restorationof the spinal disc following surgical treatment. The inventioncontemplates devices and methods for restoring the normal intervertebraldisc space height and for facilitating the introduction of biomaterialsfor use in the repair and restoration of the intervertebral disc.

[0003] The intervertebral disc is divided into two distinct regions: thenucleus pulposus and the annulus fibrosus. The nucleus lies at thecenter of the disc and is surrounded and contained by the annulus. Theannulus contains collagen fibers that form concentric lamellae thatsurround the nucleus and insert into the endplates of the adjacentvertebral bodies to form a reinforced structure. Cartilaginous endplatesare located at the interface between the disc and the adjacent vertebralbodies.

[0004] The intervertebral disc is the largest avascular structure in thebody. The disc receives nutrients and expels waste by diffusion throughthe adjacent vascularized endplates. The hygroscopic nature of theproteoglycan matrix of the nucleus operates to generate highintra-nuclear pressure. As the water content in the disc increases, theintra-nuclear pressure increases and the nucleus swells to increase theheight of the disc. This swelling places the fibers of the annulus intension. A normal disc has a height of about 10-15 mm.

[0005] There are many causes of disruption or degeneration of theintervertebral disc that can be generally categorized as mechanical,genetic and biochemical. Mechanical damage includes herniation in whicha portion of the nucleus pulposus projects through a fissure or tear inthe annulus fibrosus. Genetic and biochemical causes can result inchanges in the extracellular matrix pattern of the disc and a decreasein biosynthesis of extracellular matrix components by the cells of thedisc. Degeneration is a progressive process that usually begins with adecrease in the ability of the extracellular matrix in the centralnucleus pulposus to bind water due to reduced proteoglycan content. Witha loss of water content, the nucleus becomes desiccated resulting in adecrease in internal disc hydraulic pressure, and ultimately to a lossof disc height. This loss of disc height can cause the annulus to bucklewith non-tensile loading and the annular lamellae to delaminate,resulting in annular fissures. Herniation may then occur as ruptureleads to protrusion of the nucleus.

[0006] Proper disc height is necessary to ensure proper functionality ofthe intervertebral disc and spinal column. The disc serves severalfunctions, although its primary function is to facilitate mobility ofthe spine. In addition, the disc provides for load bearing, loadtransfer and shock absorption between vertebral levels. The weight ofthe person generates a compressive load on the discs, but this load isnot uniform during typical bending movements. During forward flexion,the posterior annular fibers are stretched while the anterior fibers arecompressed. In addition, a translocation of the nucleus occurs as thecenter of gravity of the nucleus shifts away from the center and towardsthe extended side.

[0007] Changes in disc height can have both local and global effects. Onthe local (or cellular, level) decreased disc height results inincreased pressure in the nucleus, which can lead to a decrease in cellmatrix synthesis and an increase in cell necrosis and apoptosis. Inaddition, increases in intra-discal pressure create an unfavorableenvironment for fluid transfer into the disc, which can cause a furtherdecrease in disc height.

[0008] Decreased disc height also results in significant changes in theglobal mechanical stability of the spine. With decreasing height of thedisc, the facet joints bear increasing loads and may undergo hypertrophyand degeneration, and may even act as a source of pain over time.Decreased stiffness of the spinal column and increased range of motionresulting from loss of disc height can lead to further instability ofthe spine, as well as back pain. The outer annulus fibrosus is designedto provide stability under tensile loading, and a well-hydrated nucleusmaintains sufficient disc height to keep the annulus fibers properlytensioned. With decreases in disc height, the annular fibers are nolonger able to provide the same degree of stability, resulting inabnormal joint motion. This excessive motion can manifest itself inabnormal muscle, ligament and tendon loading, which can ultimately be asource of back pain.

[0009] Radicular pain may result from a decrease in foraminal volumecaused by decreased disc height. Specifically, as disc height decreases,the volume of the foraminal canal, through which the spinal nerve rootspass, decreases. This decrease may lead to spinal nerve impingement,with associated radiating pain and dysfunction

[0010] Finally, adjacent segment loading increases as the disc heightdecreases at a given level. The discs that must bear additional loadingare now susceptible to accelerated degeneration and compromise, whichmay eventually propagate along the destabilized spinal column.

[0011] In spite of all of these detriments that accompany decreases indisc height, where the change in disc height is gradual many of the illeffects may be “tolerable” to the spine and may allow time for thespinal system to adapt to the gradual changes. However, the suddendecrease in disc volume caused by the surgical removal of the disc ordisc nucleus may heighten the local and global problems noted above.Many disc defects are treated through a surgical procedure, such as adiscectomy in which the nucleus pulposus material is removed. During atotal discectomy, a substantial amount (and usually all) of the volumeof the nucleus pulposus is removed and immediate loss of disc height andvolume can result. Even with a partial discectomy, loss of disc heightcan ensue. Discectomy alone is the most common spinal surgicaltreatment, frequently used to treat radicular pain resulting from nerveimpingement by disc bulge or disc fragments contacting the spinal neuralstructures.

[0012] In another common spinal procedure, the discectomy may befollowed by an implant procedure in which a prosthesis is introducedinto the cavity left in the disc space when the nucleus material isremoved. Thus far, the most prominent prosthesis is a mechanical deviceor a “cage” that is sized to restore the proper disc height and isconfigured for fixation between adjacent vertebrae. These mechanicalsolutions take on a variety of forms, including solid kidney-shapedimplants, hollow blocks filled with bone growth material, push-inimplants and threaded cylindrical cages.

[0013] In more recent years, injectable biomaterials have been morewidely considered as an augment to a discectomy. As early as 1962, AlfNachemson suggested the injection of room temperature vulcanizingsilicone into a degenerated disc using an ordinary syringe. In 1974,Lemaire and others reported on the clinical experience of Schulman withan in situ polymerizable disc prosthesis. Since then, many injectablebiomaterials or scaffolds have been developed as a substitute for thedisc nucleus pulposus, such as hyaluronic acid, fibrin glue, alginate,elastin-like polypeptides, collagen type I gel and others. A number ofpatents have issued concerning various injectable biomaterialsincluding: cross-linkable silk elastin copolymer discussed in U.S. Pat.No. 6,423,333 (Stedronsky et al.); U.S. Pat. No. 6,380,154 (Capello etal.); U.S. Pat. No. 6,355,776 (Ferrari et al.); U.S. Pat. No. 6,258,872(Stedronsky et al.); U.S. Pat. No. 6,184,348 (Ferrari et al.); U.S. Pat.No. 6,140,072 (Ferrari et al.); U.S. Pat. No. 6,033,654 (Stedronsky etal.); U.S. Pat. No. 6,018,030 (Ferrari et al.); U.S. Pat. No. 6,015,474(Stedronsky); U.S. Pat. No. 5,830,713 (Ferrari et al.); U.S. Pat. No.5,817,303 (Stedronsky et al.); U.S. Pat. No. 5,808,012 (Donofrio etal.); U.S. Pat. No. 5,773,577 (Capello); U.S. Pat. No. 5,773,249(Capello et al.); U.S. Pat. No. 5,770,697 (Ferrari et al.); U.S. Pat.No. 5,760,004 (Stedronsky); U.S. Pat. No. 5,723,588 (Donofrio); U.S.Pat. No. 5,641,648 (Ferrari); and U.S. Pat. No. 5,235,041 (Capello etal.); protein hydrogel described in U.S. Pat. No. 5,318,524 (Morse etal.); U.S. Pat. No. 5,259,971 (Morse et al.); U.S. Pat. No. 5,219,328(Morse et al.); and U.S. Pat. No. 5,030,215; polyurethane-filledballoons discussed in No. 60/004,710 (Felt et al.); U.S. Pat. No.6,306,177 (Felt et al.); U.S. Pat. No. 6,248,131 (Felt et al.) and U.S.Pat. No. 6,224,630 (Bao et al.); collagen-PEG set forth in U.S. Pat. No.6,428,978 (Olsen et al.); U.S. Pat. No. 6,413,742 (Olsen et al.); U.S.Pat. No. 6,323,278 (Rhee et al.); U.S. Pat. No. 6,312,725 (Wallace etal.); U.S. Pat. No. 6,277,394 (Sierra); U.S. Pat. No. 6,166,130 (Rhee etal.); U.S. Pat. No. 6,165,489 (Berg et al.); U.S. Pat. No. 6,123,687(Simonyi et al.); U.S. Pat. No. 6,111,165 (Berg); U.S. Pat. No.6,110,484 (Sierra); U.S. Pat. No. 6,096,309 (Prior et al.); U.S. Pat.No. 6,051,648 (Rhee et al.); U.S. Pat. No. 5,997,811 (Esposito et al.);U.S. Pat. No. 5,962,648 (Berg); U.S. Pat. No. 5,936,035 (Rhee et al.);and U.S. Pat. No. 5,874,500 (Rhee et al.); chitosan in U.S. Pat. No.6,344,488 to Chenite et al.; a variety of polymers discussed in U.S.Pat. No. 6,187,048 (Milner et al.; recombinant biomaterials in No.60/038,150 (Urry); U.S. Pat. No. 6,004,782 (Daniell et al.); U.S. Pat.No. 5,064,430 (Urry); U.S. Pat. No. 4,898,962 (Urry); U.S. Pat. No.4,870,055 (Urry); U.S. Pat. No. 4,783,523 (Urry et al.); U.S. Pat. No.4,783,523 (Urry et al.); U.S. Pat. No. 4,589,882 (Urry); U.S. Pat. No.4,500,700 (Urry); U.S. Pat. No. 4,474,851 (Urry); U.S. Pat. No.4,187,852 (Urry et al.); and U.S. Pat. No. 4,132,746 (Urry et al.); andannulus repair materials described in U.S. Pat. No. 6,428,576 toHaldimann.

[0014] These references disclose biomaterials or injectable scaffoldsthat have one or more properties that are important to disc replacement,including strong mechanical strength, promotion of tissue formation,biodegradability, biocompatibility, sterilizability, minimal curing orsetting time, optimum curing temperature, and low viscosity for easyintroduction into the disc space. The scaffold must exhibit thenecessary mechanical properties as well as provide physical support. Itis also important that the scaffold be able to withstand the largenumber of loading cycles experienced by the spine. The biocompatibilityof the material is of utmost importance. Neither the initial materialnor any of its degradation products should elicit an unresolved immuneor toxicological response, demonstrate immunogenicity, or expresscytoxicity.

[0015] Generally, the above-mentioned biomaterials are injected asviscous fluids and then cured in situ. Curing methods includethermosensitive cross-linking, photopolymerization, or the addition of asolidifying or cross-linking agent. The setting time of the material isimportant—it should be long enough to allow for accurate placement ofthe biomaterial during the procedure yet should be short enough so asnot to prolong the length of the surgical procedure. If the materialexperiences a temperature change while hardening, the increase intemperature should be small and the heat generated should not damage thesurrounding tissue. The viscosity or fluidity of the material shouldbalance the need for the substance to remain at the site of itsintroduction into the disc, with the ability of the surgeon tomanipulate its placement, and with the need to assure complete fillingof the intradiscal space or voids.

[0016] Regardless of the injectable scaffold material used, it iscritical that the completed procedure restore the disc height. It isthus important that the proper disc height be maintained while thebiomaterial is being introduced into the intradiscal space. Ideally, thedisc height will be restored to levels equivalent to the heights of theadjacent discs and representative of a normal spinal disc height for theparticular patient.

[0017] However, if disc height is not re-established prior tointroduction of the scaffold material, it will become impossible toreplace the lost disc volume and at least restore the disc height towhat it was prior to the discectomy. Failure to hold a proper discheight as the biomaterial is introduced and cured in situ can eventuallylead to a collapse of the disc space. This phenomenon is illustrated bya comparison of a proper intervertebral disc height in FIG. 1a versus areduced disc height in FIG. 1b. The reduced disc height of FIG. 1b willordinarily follow a substantially complete discectomy, unless theadjacent vertebrae are distracted. The patient can be placed in certainpositions that tend to open the disc space, particularly at theposterior side of the disc D. However, it has been found that even withhyper-flexion of the spine the intervertebral space does not approachits proper volume, and consequently the intervertebral height does notapproach the proper disc height of FIG. 1a.

[0018] Prior procedures for the implantation of a curable discprosthesis have relied upon the physical positioning of the patient orupon pressurized injection of the biomaterial to obtain some degree ofdistraction. However, these prior approaches do not achieve repeatablerestoration of proper anatomical disc height, either during the surgicalprocedure or afterwards. Consequently, there remains a need for a methodand system that provides a high degree of assurance that a proper discheight will be established and maintained when the intervertebral discis replaced or augmented by an injectable biomaterial.

SUMMARY OF THE INVENTION

[0019] In order to address the unresolved needs of prior spinalprocedures, the present invention contemplates a method for injecting afluent material into a disc space. The method includes the steps ofcreating a portal in the annulus pulposus in communication with theintradiscal space and impacting a cannulated distractor into the portal.In accordance with one feature of the invention, the distractor isconfigured to distract the vertebrae adjacent the intradiscal space andto establish a disc space height between the adjacent vertebrae. Themethod includes the further step of introducing the fluent material intothe intradiscal space through a lumen of the cannulated distractor whilethe distractor maintains the established disc space height.

[0020] In certain embodiments, the inventive method includes the step ofperforming a discectomy after the portal is created, in which thediscectomy forms a cavity within the intradiscal space. In thisembodiment, the step of impacting a cannulated distractor includespositioning the distractor so that the lumen is in communication withthe cavity, and the step of introducing the fluid includes introducingthe fluid into the cavity. The discectomy can be a total discectomy inwhich substantially all of the nucleus pulposus is removed from the discspace.

[0021] In a further feature of the invention, the fluent material is acurable biomaterial that is particularly suited as a disc replacement oraugmentation material. In this case, the step of introducing the fluentmaterial can include maintaining the distractor in its impacted positionuntil the biomaterial cures in situ. In other words, the cannulateddistractor maintains the adjacent vertebrae in their distracted positionuntil the biomaterial has set. In this way, the proper disc height canbe maintained and retained once the biomaterial has set and thedistractor removed.

[0022] In certain embodiments, the fluent material can be introducedinto the disc cavity under pressure. In another feature of the inventionthat is particularly useful where the fluent material is under pressure,the cannulated distractor is configured to seal the portal when thedistractor is impacted therein. In some embodiments, the distractor hasa portion sized to substantially block or seal the annular portal. Inother embodiments, the distractor includes a sealing feature that bearsagainst the adjacent vertebrae and/or the annulus fibrosus materialsurrounding the portal. The sealing feature can be integral with thecannulated distractor or can include a separate component, such as aseal ring, mounted on the distractor.

[0023] In still another aspect of the invention, and again one that isparticularly suited where the fluent material is under pressure, a ventis provided in the cannulated distractor. Thus, the fluent material canbe introduced into the intradiscal space until the fluent material seepsfrom the vent. Thus, the vent can provide an immediate indication thatthe disc cavity is full.

[0024] In some embodiments of the invention, the cannulated distractoris engaged to a fluid injector apparatus. This apparatus can be in avariety of forms, including a pump, a syringe and a gravity feed system.

[0025] In other embodiments, the step of introducing the fluent materialincludes extending an tube through the lumen in the cannulateddistractor, with the tube fluidly connected to a source of the fluentmaterial. The tube can be manipulated through the distractor lumen todirect the fluent material to specific locations within the disc cavity.For instance, the tube can be moved through a seeping motion so that thefluent material is completely dispersed throughout the disc space. Atthe same time, the tube can be gradually withdrawn from the distractorlumen as the fluent material nears the lumen opening.

[0026] In a preferred embodiment, a seal is provided between the tubeand the lumen. A vent can then be provided separate from the lumen sothat the fluent material can seep from the vent to indicate that thecavity is full.

[0027] In another embodiment of the invention, a device for injecting afluent material into a disc space comprises a distraction member havingopposite surfaces configured to distract adjacent vertebrae to the discspace. The distraction member has a proximal end and a distal endportion, in which at least the distal end portion configured to bedisposed within the disc space. The distraction member further defines afluid passageway between the proximal end and the distal end portion,the passageway having an opening at the proximal end and at the distalend portion. In some embodiments, the distraction member can include afitting associated with the proximal end of the distraction member forfluidly connecting the distraction member to a source of the fluentmaterial.

[0028] In accordance with another aspect of the invention, the devicefurther comprises an elongated cannula defining a lumen therethrough.The cannula can have a first fitting at one end thereof configured forfluid tight connection to the fitting of the distraction member, and asecond fitting at an opposite end thereof configured for fluidconnection to a source of the fluent material. In specific embodiments,the distraction member is integral with the cannula and the secondfitting is the fitting associated with the proximal end of thedistraction member. In other embodiments, the distraction member isremovable from the cannula.

[0029] In a preferred embodiment, at least the distal end portion of thedistraction member is bullet-shaped. In alternative embodiments, thedistal end portion of is wedge-shaped with opposite substantially flatsides, cruciate-shaped, I-beam shaped and C-shaped.

[0030] The fluid passageway of the distraction member includes a centrallumen with a number of openings communicating therewith. The openingscan be arranged in the variously shaped distal end portion to direct thefluent material to appropriate locations within the disc cavity. Thedistraction member can also define a vent opening separate from thefluid passageway. In certain embodiments, the fluid passageway can be inthe form of interconnected interstices throughout the distraction membermaterial.

[0031] In the preferred embodiment, the distraction member is formed ofa biocompatible material, such as stainless steel or titanium. Inalternative embodiments, other biocompatible materials can be used, suchas polymeric materials and even bioresorbable materials. In accordancewith one aspect, the distraction member is configured to be removed fromthe disc space once the fluent material has been introduced into thedisc cavity, and has cured, if necessary. In other aspects, thedistraction member is configured to remain within the disc space, mostpreferably if the member is formed of a bioresorbable material.

[0032] The distraction member can include a sealing element associatedwith a proximal portion of the distal end portion, wherein the sealingelement is configured to provide a substantially fluid-tight seal withinthe disc space. The sealing element can include a number of seal ringsdisposed on the distal end portion. The seal rings can be integral withthe distal end portion or can be elastomeric rings mounted on the distalend portion, for example.

[0033] It is one object of the invention to provide a system and devicefor maintaining and enforcing a proper intervertebral spacing or discheight when a disc prosthesis is introduced into a cavity within theintradiscal space. Another object is achieved by features of theinvention that allow introduction of a fluent material into the discspace while maintaining the adjacent vertebrae distracted and the discheight intact.

[0034] Other objects and certain benefits of the invention can bediscerned from the following written description and accompanyingfigures.

DESCRIPTION OF THE FIGURES

[0035]FIGS. 1a-1 b are lateral views of a disc and adjacent vertebraeshowing a proper intervertebral disc height (FIG. 1a) and a reduced discheight (FIG. 1b) following a substantially complete discectomy.

[0036]FIG. 2 is a lateral view a disc and adjacent vertebrae with aguide wire placed in accordance with one aspect of the presentinvention.

[0037]FIG. 3 is a sagittal view of the disc space shown in FIG. 2 with atrephine forming a portal in the annulus fibrosus of the disc.

[0038]FIG. 4 is a sagittal view of the disc space shown in FIG. 3 with atissue extraction device positioned within the nucleus pulposus of thedisc.

[0039]FIG. 5 is a sagittal view of the disc space shown in FIGS. 2-4with a cannulated distractor in accordance with one embodiment of thepresent invention.

[0040]FIG. 6 is a side view of a cannulated distractor in accordancewith one embodiment of the present invention.

[0041]FIG. 7 is a lateral view of the disc space shown in FIGS. 2-5 withthe cannulated distractor of FIG. 6 positioned within the disc space.

[0042]FIG. 8 is a perspective view of a distraction tip forming part ofthe cannulated distractor shown in FIGS. 6 and 7.

[0043]FIG. 9 is a perspective view of a distraction tip according analternative embodiment of the invention.

[0044]FIG. 10 is a side view of an injector apparatus for use in oneembodiment of the invention.

[0045]FIG. 11 is lateral view of a disc space with a cannulateddistractor in accordance with a further embodiment of the invention.

[0046]FIG. 12 is a cross-sectional view of a cruciate distraction tipaccording to one embodiment of the cannulated distractor of the presentinvention.

[0047]FIG. 13 is a cross-sectional view of an I-beam shaped distractiontip according to another embodiment of the cannulated distractor of thepresent invention.

[0048]FIG. 14 is a cross-sectional view of a C-shaped distraction tipaccording to a further embodiment of the cannulated distractor of thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0049] For the purposes of promoting an understanding of the principlesof the invention, reference will now be made to the embodimentsillustrated in the drawings and described in the following writtenspecification. It is understood that no limitation to the scope of theinvention is thereby intended. It is further understood that the presentinvention includes any alterations and modifications to the illustratedembodiments and includes further applications of the principles of theinvention as would normally occur to one skilled in the art to whichthis invention pertains.

[0050] The present invention contemplates a procedure and device that isimplemented following removal of a portion or substantially all of thenatural nucleus pulposus of an intervertebral disc. One importantpurpose of the invention is to maintain the proper disc height duringthe introduction of a biomaterial that is intended to replace theremoved nuclear material. Removal of disc material can be accomplishedchemically, such as by the use of Chymopapain. However, the more commonapproach is by discectomy, which can be conducted as an open surgicalprocedure, via microscope-assisted visualization, or throughpercutaneous access.

[0051] A typical percutaneous discectomy procedure is illustrated inFIGS. 2-4. In the first step, a guide wire G is directed into anaffected disc D between two vertebrae, such as the L2 and L3 lumbarvertebrae. As shown in FIG. 3, the guide wire G penetrates the annulusfibrosus A and the nucleus pulposus N, and it preferably anchored atopposite sides of the annulus A. The guide wire G can be positioned andplaced under indirect vision, such as fluoroscopy, or stereotactically,or using other known procedures for properly orienting the guide wirewithin the spinal disc D. The procedure shown in the figures utilizes aposterior approach, which is preferable for implementation of thepresent invention. Of course, other approaches may be utilized for thediscectomy in accordance with known surgical procedures. In addition,the access location may be dictated by the location of a fissure orherniation of the disc.

[0052] A trephine T is advanced over the guide wire and driven throughthe annulus A, thereby forming a portal into the disc nucleus. As shownin FIG. 4, a tissue removal device R can be advanced through thetrephine T or through a working channel cannula aligned with the discportal. The device R can then be used to remove all or part of thenucleus N of the disc D. As depicted in dashed lines in FIG. 4, a secondtrephine T′ can be used to create a second annular portal to facilitatecomplete removal of the nucleus pulposus of the disc. The tissue removaldevice R can be of a variety of types, such as a rongeur, tissuemorcellator, rotary and/or reciprocating vacuum-assisted cutter, andeven a chemical introducer to direct a chemical such as Chymopapain intothe nuclear space. Removal of the nucleus leaves a cavity C (see FIG. 5)surrounded by the substantially intact annulus A The present inventioncontemplates the introduction of a biomaterial into the disc cavity Cthat is capable or restoring disc height and preferably substantiallynormal disc function. For instance, any of the biomaterials discussedabove can fill the newly formed cavity. In accordance with the preferredembodiment, the biomaterial is a fluid with an appropriate flowabilityand/or viscosity. In particular, the biomaterial must have sufficientflowability to permit relatively easy introduction into the disc cavityC, but with sufficient viscosity to hold its shape within the disc.Since the material being used to fill the disc cavity C is a fluid, thepresent invention provides means for holding a proper disc height as thematerial flows into the cavity, to thereby ensure that the cavity isfilled—i.e., that the volume of implant biomaterial is the same as thevolume of nucleus pulposus removed in the discectomy. Moreover, themethods and devices of the invention provide a means for maintaining thecavity volume as the biomaterial transforms to its solid state.

[0053] Thus, in accordance with one embodiment of the invention, acannulated distractor 10 is provided as shown in FIGS. 5-8. Thedistractor 10 includes a distal end 12 that extends into the disc cavityC and a proximal end 14 that is configured to engage a device forinjecting the biomaterial into the disc space. The distractor 10includes a cannula 11 that terminates in a distraction tip 18 at thedistal end of the device. A lumen 16 is defined along the entire lengthof the device from the proximal end 14 to the and through thedistraction tip 18. The distraction tip 18 is sized to extend throughthe portal formed in the disc annulus A (see FIG. 3). The distractor 10can include a shoulder 20 proximal to the distraction tip 18, in whichthe shoulder is sized to prevent passage through the annular portal. Theshoulder 20 can operate to limit the distance that the distraction tip18 extends into the disc cavity C. The distractor 10 can be providedwith means for temporarily fixing the distractor in position orsupporting the distractor on the adjacent vertebrae.

[0054] As shown in FIG. 7, the distraction tip 18 is intended to beinserted through the annular portal and is configured to restore theappropriate intradiscal height in the cavity C. Thus, in one embodiment,the distraction tip 18 can include a tapered leading portion 24. Thisleading portion 24 can be introduced into the cavity C and as the tip isadvanced further into the cavity the leading portion will graduallydistract the adjacent vertebrae as the leading portion 24 bears againstthe disc endplates E. In a specific embodiment, the tapered portion 24can be substantially bullet-shaped, as shown in FIG. 8. With thisconfiguration, the distraction tip 18 can have any rotationalorientation when the tip is inserted through the annular portal.

[0055] Alternatively, the distraction tip can be configured like the tip40 shown in FIG. 9. With this embodiment, the tip includes opposinggenerally flat sides 50 and intermediate edges 52 of the wedge portion42. The tip 40 can be introduced into the disc space with the flat sides50 of the wedge facing the disc endplates E. Once the tip is fullywithin the disc cavity C, the tip can be rotated so that the edges 52contact and distract the endplates. The edges 52 themselves can bewedge-shaped, having a greater width at their proximal end than at theirdistal end.

[0056] Returning to FIGS. 6-8, in accordance with one feature of theinvention, the distraction tip 18 includes a number of side orifices 30and an end orifice 32 that all communicate with the central lumen 16. Asdepicted in FIG. 7, the orifices 30, 32 provide an exit path for fluidinjected through the lumen 16. Preferably, the orifices are oriented tobe unobstructed by the vertebral endplates E. The distraction tip 40shown in FIG. 9 is also provided with side orifices 46 in the flat sides50 and an end orifice 48. With this embodiment, the edges 52 need notinclude orifice(s) because the edges will be occluded by contact theendplates.

[0057] Since fluid is intended for introduction through the distractiontip 30, it is preferable that some feature be provided to ensure asubstantially fluid-tight seal at the entrance to the disc cavity Cthrough the annular portal. Thus, in one embodiment of the invention,the distraction tip 30 can include annular rings 26 that are intended tobear against the disc endplates E and/or the disc annulus A in a sealingrelationship. The rings 26 can be integral with the distraction tip 30,or can be separate components mounted on the distraction tip, such as inthe form of elastomeric seal rings. The seal rings can be mounted withinannular grooves formed in the distraction tip.

[0058] The distractor 10 includes a fitting 36 defined at the proximalend 14 of the cannula 11. The fitting 36 provides means for making afluid-tight connection with a device adapted to inject the biomaterialinto the disc. One exemplary device 70 is shown in FIG. 10. The injector70 includes a chamber 72 for storage of the biomaterial. In some cases,the chamber 72 may constitute multiple chambers where the injectablebiomaterial is obtained by mixing various constituent materials. Forinstance, certain materials may be curable in situ and may requirecombining a curing agent with a base material. To facilitate mixing ofthe biomaterial constituents, the injector 70 can include a mixingchamber 74. A manual control 76 can be provided that forces the contentsof the chamber 72 into the mixing chamber 74. Alternatively, theinjector 70 can incorporate a mechanism that drives the fluid from theinjector under pressure, such as a syringe or a pump.

[0059] The injector 70 includes a fitting 80 that is configured forfluid-tight engagement with the fitting 36 of the cannulated distractor10. In a preferred embodiment, the two fittings 36, 80 represent matingcomponents of a LUER® fitting. The injector can include a nozzle 78 thatextends into the cannula 11, or more specifically into the lumen 16,when the injector 70 is engaged to the cannulated distractor. A grip 82can be provided to allow manual stabilization of the injector.

[0060] As explained above, the cannulated distractor 10 of the presentinvention may be utilized after a discectomy procedure. For purposes ofillustration, it has been assumed that a total discectomy has beenperformed in which substantially all of the nucleus pulposus has beenremoved, leaving a disc cavity C as shown in FIG. 5. Of course, theprinciples of the invention can apply equally well where only a portionof the disc nucleus has been removed through a partial discectomy. If abilateral approach has been used (as represented by the first and secondtrephines T and T′), one of the annular portals can be sealed with amaterial compatible to the disc annulus fibrosus. When the nucleus hasbeen cleared, the guide wire G can be repositioned within the disc D,again preferably using known guidance and positioning instruments andtechniques. The cannulated distractor 10 can then be advanced over theguide wire until the distraction tip 18 is properly situated within thenuclear cavity C. Preferably, the proper depth for the distraction tip18 can be determined by contact of the shoulder 20 with the outerannulus A, or by contact of an associated depth feature with theadjacent vertebral bodies.

[0061] With the distraction tip 18, the tapered portion 24 graduallyseparates the adjacent vertebral endplates E as the distraction tip isdriven further into the disc space. A mallet, impactor or other suitabledriver can be used to push the tapered portion 24 into position againstthe natural tension of the disc annulus. It is understood that the goalof this step is to fully distract the intervertebral space to a properdisc height for the particular spinal level. For instance, for the L2-L3disc space, the appropriate disc height may be 13-15 mm, so that thedistraction tip is positioned within the cavity C to achieve this amountof distraction. As shown in FIG. 5, preferably only one cannulateddistractor 10 is utilized, since the distraction tip 18 necessarilyoccupies a certain portion of the volume of the cavity C. However, asecond cannulated distractor and associated distraction tip may benecessary (such as through a second annular portal as shown in FIG. 4)to achieve the proper disc height.

[0062] It should be understood that the process thus far would besimilar for the distraction tip 40. However, unlike the tapereddistraction tip 18, the distraction tip 40 requires an additional stepto distract the disc space. Specifically, the distraction tip 40 isinitially inserted with its flat sides 50 facing the endplates E. Thetip must then be rotated until the edges 52 bear against and support theendplates. The flat sides 50 can include an angled transition to theedges, or the edges 52 can be rounded to facilitate the distraction asthe distraction tip is rotated in situ.

[0063] When the distraction tip, such as tip 10, is inserted to itsproper depth within the disc cavity C, the annular portal is sealed,whether by contact with the shoulder 20, or by engagement of the rings26 with the endplates E or the interior of the annular portal. At thispoint, the biomaterial fluid can be injected into the cannulateddistractor, and specifically into the lumen 16. To accomplish this step,the injector, such as injector 70, can be mated with the fitting 36 atthe proximal end 14 of the cannulated distractor. Optimally, the guidewire G is removed and the fitting 80 of the injector engages the fitting36. The nozzle 78 extends into the lumen 16. The nozzle can be sized sothat the exit end of the nozzle is near or within the distraction tip18. At this point, the injector 70 can be actuated in accordance withits construction so that the biomaterial fluid is displaced from theinjector and into the lumen 16. The biomaterial exits through theorifices 30, 32 in the distraction tip 18 to fill the cavity C. Theorifices 30, 32 are preferably positioned and sized to achieve completeand rapid dispersion of the biomaterial throughout the cavity. Again,the goal of this step of the process is to completely fill the entirevolume of the cavity, or to replace the entire volume of nucleuspulposus removed during the discectomy. Where the fluid biomaterial isan in situ curable or settable material, time may also be of the essenceto ensure a homogeneous mass once the material is completely cured.

[0064] It should be apparent that the distraction tip 18, 40 maintainsthe proper disc height while the biomaterial is injected. The tip can beretained in position until the injected material cures or sets. Once thematerial has sufficiently cured, the distraction tip 18, 40 can beremoved. Since the distraction tip occupies a certain volume, additionalbiomaterial can be injected through the tip as it is being withdrawn, ifrequired, thereby filling the gap left by the tip.

[0065] In certain embodiments, the distraction tip 18 can be a modularand removable from the cannula 11, as shown in FIG. 8. Thus, the tip 18and cannula 11 can be provided with a removable mating element 19, suchas a press-fit (as shown in FIG. 9) or a threaded or LUER® type fitting(not shown) as would occur to a person of skill in this art. A removabledistraction tip can serve several purposes. In one purpose, the injectedbiomaterial may require a lengthy curing time. While the material iscuring, it is of course necessary to keep the distraction tip inposition to maintain the proper disc height. However, it may not benecessary to retain the other components of the system in position, suchas the injector 70 and cannula 11. A modular distraction tip allows thecannula 11 to be removed while the tip remains in position, acting as adisc spacer while the biomaterial cures.

[0066] In another purpose, a number of differently sized tips can bemounted to a commonly sized cannula. Each patient has a different spinalanatomy, which means the appropriate disc height at a given spinal levelmay vary between patients. Moreover, the disc height can vary withspinal level. Thus, a plurality of differently sized distraction tips 18can be provided to ensure proper spacing across the spinal disc D.

[0067] Another purpose behind a removable distraction tip 18 is achievedby embodiments in which the tip is formed of a biocompatible materialthat allows the tip to remain resident within the disc space. In thisembodiment, the distraction tip material must be compatible with thebiomaterial used to replace the natural nucleus. For instance, if thebiomaterial is only intended to restore disc height, but not the naturalbiomechanical properties of the natural nucleus, then the material ofthe distraction tip 18 may provide a generally rigid scaffolding. On theother hand, and most preferably, the injected biomaterial is intended toemulate the biomechanical characteristics of the disc to allow thespinal segment to operate as close to a normal spinal segment aspossible. In this instance, a rigid scaffold would of course frustratethe normal flexion, compression and torsional responses of the disc.Thus, the distraction tip 18 in embodiments where the tip is left insitu can be formed of a biodegradable or bioresorbable material thatabsorbs into the matrix of the cured biomaterial forming the discnucleus prosthesis.

[0068] Whether the distraction tip is removed or remains within the discspace, it is preferable that the tip occupy as little volume aspossible. On the other hand, the distraction tip must be sufficientlystrong to sustain the compression loads that it will face whiledistracting adjacent vertebrae and holding the disc space height whilethe injected biomaterial cures. In the specific embodiments shown inFIGS. 5 and 7, the distraction tip 18 is shown traversing across asubstantial portion of the nuclear cavity C. Alternatively, thedistraction tip can have a reduced length from the shoulder 20 so thatthe tip extends only partially into the cavity. Distraction of the discspace can be abetted by certain positions of the patient on theoperating table where, for instance, the anterior aspect of the discspace is naturally distracted by the position of the spine. Properdistraction of the disc space may be better accommodated by an anteriorapproach, rather than the posterior approach shown in FIGS. 5 and 7.

[0069] In alternative embodiments, the distraction tip can assume a widerange of geometries, some dictated by the annular portal formed duringthe discectomy procedure. In the embodiment of FIGS. 5-8, a circularannular portal has bee created and a circular distraction tip 18utilized to seal the portal. In some cases, a planar or wedge-shapeddistraction tip, similar to the tip 40 shown in FIG. 9, can be utilizedwhere the opening through the annulus has an area greater than the tipitself. In these cases, the extra space between the tip and the interiorsurface of the portal can provide an opening for a direct visualizationinstrument, or some other appropriate instrument. Preferably, thisapproach is better suited where the biomaterial is not injected underpressure, such as cases where a gravity feed is employed (see FIG. 11and associated discussion below).

[0070] In other cases, surgeons perform the discectomy throughrectangular or cruciate portals in the disc annulus. A complementaryshaped distraction tip can be utilized to conform to and fill theannular portal. For instance, the distraction tip can assume theconfiguration shown in FIGS. 12-14. A cruciate-shaped tip 55 is shown inFIG. 12 with a central lumen 56 communicating with a number of openings56. It is understood that the arms of the cruciate-shaped tip can have athinner cross-section than shown in the figure, provided they aresufficiently strong to support the adjacent vertebrae in their properdistracted position. Likewise, the openings 56 can be distributed in avariety of patterns through the hub and legs of the cruciate shape.

[0071] An I-beam distraction tip 60 is shown in FIG. 13 having a centrallumen 61 communicating with a number of openings 62. The distraction tip63 in FIG. 14 has a C shape and includes a lumen 64 and openings 65.These two beam configurations provide sufficient support for thenecessary distraction. Again, the thickness of the arms of the beams canbe reduced as necessary to minimize the cross-section of the distractiontip 60, 63.

[0072] Regardless of the overall configuration of the distraction tip,it is most preferable that volume of the tip within the nuclear cavity Cbe minimized. The bullet-shaped tip, such as tip 18, may be lessdesirable from that standpoint, while the wedge type, such as tip 40,may be preferable. In addition, regardless of the overall configuration,the distraction tip must communicate with the lumen 16 and must providesome means for discharge of the biomaterial fluid through the tip. Inthe illustrated embodiments, the distraction tips 18, 40 includeorifices 30, 31 and 46, 48, respectively, that communicate with thecorresponding lumens 16, 44. Alternatively, the distraction tips can bein the form of an open scaffold or skeletal framework. Again, thescaffold or framework must be sufficiently strong, especially incompression, to properly distract the disc space and hold the discheight for an appropriate length of time. In some embodiments, thedistraction tip can be formed of a material having interconnectedinterstices, such as a porous material. The porous distraction tip canpresent a solid scaffold with a multitude of fluid flow paths throughthe material. The porous material can be a metal, such as a poroustantalum; however, a porous polymer, such as polylactic acid, ispreferred so that the scaffold does not obscure visualization of thedisc space after the procedure is completed.

[0073] In the procedures discussed above, the distraction tip has beendescribed as providing an avenue for the injection of a biomaterial intothe nuclear cavity C following a discectomy procedure. The distractiontips of the present invention serve equally well as a conduit for theintroduction of other fluids to the disc space. For instance, thedistraction tips can be used to inject a biomaterial such as thematerial disclosed in provisional application Serial No. 60/336,332,entitled “Pretreatment of Cartilaginous Endplates Prior to Treatment ofthe Intervertebral Disc with an Injectable Biomaterial”, mentionedabove, the disclosure of which is incorporated herein by reference. Thisprovisional application discloses materials for the pretreatment of thedisc endplates, for instance, to improve the biological functioning of adegenerative disc. The cannulated distractors of the present invention,such as distractor 10, can be initially used for the disc pretreatmentsdisclosed in the above-mentioned provisional application. Once thepretreatment has been completed, the cannulated distractor can then beused for the injection of the curable biomaterial.

[0074] Likewise, the present inventive cannulated distractor can be usedfor multiple fluid injections, including multiple injections to effectcuring of a biomaterial within the nuclear cavity C. For instance,certain biomaterials may include a first constituent that is introducedinto the disc space, followed by a second constituent or curing agent.The second constituent can initiate curing of the resulting composition.

[0075] An alternative embodiment of the invention is depicted in FIG.11. In this embodiment, a cannulated distractor 85 is provided thatincludes a generally frusto-conical distraction tip 86 and a shoulder87. The tip 86 is configured to act as a wedge to distract the discspace as the cannulated distractor 86 is impacted into the disc space.The shoulder 87 acts as a stop against the adjacent vertebral bodies tolimit the distance that the tip is driven into the disc space.Preferably, the distraction tip 86 has a length from the shoulder 87 toits distal end that is sufficient to span the length of the portal inthe disc annulus A, but is limited in its extent into the nuclear cavityC. With this embodiment, the distraction tip 86 does not displace anysignificant volume within the cavity C.

[0076] The cannulated distractor 85 defines a lumen 88 extending theentire length of the distractor. The lumen 88 is sized to receive aninjection tube 94 therethrough. The injection tube 94 can include afitting 96 for engaging an injection apparatus 98. The fitting 96 can beof any suitable type, such as the LUER® fitting mentioned above. Theinjection apparatus can be similar to the injector 70 shown in FIG. 10,or can assume a variety of configurations for the introduction of afluid into the disc cavity. In one embodiment of the invention, thebiomaterial fluid is introduced into the cavity by way of gravity feed.In this instance, the injection apparatus 98 can be simply in the formof a reservoir with an atmospheric vent to allow the biomaterial to flowdownward into the disc space by gravity alone. Of course, the patientmust be properly presented to accommodate gravity filling of the disccavity C.

[0077] In this embodiment, the cannulated distractor 85 operates as asupport or guide for the injection tube 94. The tube 94 can be in theform of a smooth tipped, relatively large gauge needle that is sized toaccommodate optimum flow of the biomaterial into the disc space. Thetube 94 can be introduced through and gradually withdrawn from thecannulated distractor 85 (as indicated by the arrow in FIG. 11) as thebiomaterial flows into the cavity C. In addition, the diameter of thetube 94 can be sized relative to the diameter of the lumen 88 so thatthe discharge opening 95 of the tube 94 can be pivoted with a sweepingmotion through the cavity C. This aspect of this embodiment facilitatescomplete direct filling of the disc cavity C with the biomaterial. Wherethe cannulated distractor is used to introduce pre-treatment materials,such as those discussed above, this feature allows positioning of thedischarge opening 95 to direct the pre-treatment materials where theyare needed.

[0078] In certain embodiments, the lumen 88 can be provided with a seal89, which can be in the form of an elastomeric seal ring. The seal 89can form a fluid-tight seal around the injection tube 94, which can beespecially important where the biomaterial is injected under pressure.In addition, the seal 89 can operate as a form of joint to support theinjection tube 94 as the discharge opening 95 is manipulated within thedisc cavity.

[0079] In another feature of the invention, the cannulated distractorcan provide a vent for the discharge of excess biomaterial when the disccavity C is full. The vent is particularly useful where the biomaterialis introduced under gravity feed. In one specific embodiment, a venthole 92 is provided in the distractor 85. When the disc cavity is full,the biomaterial will seep through the vent opening 92, providing adirect visual indication that the cavity is full. Preferably, the ventopening 92 includes a tube that projects away from the cannulateddistractor 85 to improve the visibility of the vent in situ.Alternatively, the vent can be formed by a difference in diameterbetween the injection tube 94 and the lumen 88, and in the absence ofthe seal 89.

[0080] The vent 92 is well-suited to procedures involving gravity feedof the biomaterial into the disc space. However, the vent can also beuseful where the material is fed under pressure. For example, the vent92 can be maintained initially open as the biomaterial is injected intothe cavity C through the injection tube 94. When the cavity iscompletely full, biomaterial will seep from the vent 92. As this point,the vent can be closed and additional biomaterial injected into the discspace to increase the pressure within the cavity C. The seeping throughthe vent provides an immediate indication that the cavity is full, andcan provide a starting point for the introduction of a calibrated amountof additional biomaterial to achieve a proper cavity pressure.

[0081] With each of the embodiments, once the biomaterial has cured andthe cannulated distractor removed, the portal or portals in the discannulus can be filled to prevent herniation of the newly formedprosthetic disc material. The annular portal can be sealed with anysuitable material, such as fibrin glue, or a polymerizable material, orthe like. The material used to seal the annulus should be sufficientlystrong to remain intact as the intradiscal pressure is increased due tohydration or biomechanical movement of the spine.

[0082] In accordance with certain embodiments, the cannulateddistractors, and particularly the distraction tips, described above canbe formed a variety of bio-compatible materials. As explained above thedistraction tips must be sufficient strong to maintain properdistraction of the disc space until the biomaterial has been fullyinjected and cured, if necessary. In certain embodiments, thedistraction tips are formed of a bio-compatible metal, such as stainlesssteel or titanium. In other embodiments, the distraction tips are formedof a polymer or plastic that is preferably radiolucent to permitvisualization of the distraction tip in situ to verify the position ofthe component.

[0083] While the invention has been illustrated and described in detailin the drawings and foregoing description, the same should be consideredas illustrative and not restrictive in character. It is understood thatonly the preferred embodiments have been presented and that all changes,modifications and further applications that come within the spirit ofthe invention are desired to be protected.

What is claimed is:
 1. A method for injecting a fluent material into adisc space comprising the steps of: creating a portal in the annuluspulposus in communication with the intradiscal space; impacting acannulated distractor into the portal, the distractor configured todistract the vertebrae adjacent the intradiscal space and to establish adisc space height between the adjacent vertebrae; and introducing thefluent material into the intradiscal space through a lumen of thecannulated distractor while the distractor maintains the establisheddisc space height.
 2. The method for injecting a fluent material into adisc space according to claim 1, further comprising: the step ofperforming a discectomy after the step of creating a portal, thediscectomy forming a cavity within the intradiscal space; wherein thestep of impacting a cannulated distractor includes positioning thedistractor so that the lumen is in communication with the cavity; andwherein the step of introducing the fluid includes introducing the fluidinto the cavity.
 3. The method for injecting a fluent material into adisc space according to claim 2, wherein the discectomy is a totaldiscectomy in which substantially all of the nucleus pulposus is removedfrom the disc space.
 4. The method for injecting a fluent material intoa disc space of claim 2, wherein the fluent material is a curablebiomaterial and the step of introducing the fluent material includesmaintaining the distractor in its impacted position until thebiomaterial cures in situ.
 5. The method for injecting a fluent materialinto a disc space of claim 1, wherein the step of introducing the fluentmaterial includes introducing the fluent material under pressure.
 6. Themethod for injecting a fluent material into a disc space of claim 5,wherein the cannulated distractor is sized to seal the portal when thedistractor is impacted therein.
 7. The method for injecting a fluentmaterial into a disc space of claim 1, further comprising the step ofproviding a vent in the cannulated distractor, wherein the step ofintroducing the fluent material includes introducing the material intothe intradiscal space until the fluent material seeps from the vent. 8.The method for injecting a fluent material into a disc space of claim 1,wherein the step of introducing the fluent material includes: fluidlyengaging the cannulated distractor to a fluid injector apparatus; andactuating the apparatus to inject the fluent material through the lumenof the cannulated distractor.
 9. The method for injecting a fluentmaterial into a disc space of claim 1, wherein the step of introducingthe fluent material includes: extending an tube through the lumen in thecannulated distractor, the tube fluidly connected to a source of thefluent material; and introducing the fluent material through the tubeinto the intradiscal space.
 10. The method for injecting a fluentmaterial into a disc space of claim 9, wherein the step of extending thetube through the lumen includes providing a seal between the tube andthe lumen.
 11. The method for injecting a fluent material into a discspace of claim 9, wherein the step of introducing the fluent materialthrough the tube includes manipulating the tube so that the dischargeopening of the tube sweeps through the intradiscal space while thefluent material is introduced through the tube.
 12. The method forinjecting a fluent material into a disc space of claim 9, wherein thestep of introducing the fluent material through the tube includesgradually withdrawing the tube from the lumen while the fluent materialis introduced through the tube.
 13. A device for injecting a fluentmaterial into a disc space comprising: a distraction member havingopposite surfaces configured to distract adjacent vertebrae to the discspace, the distraction member having a proximal end and a distal endportion, at least the distal end portion configured to be disposedwithin the disc space; a fluid passageway defined between said proximalend and said distal end portion, said fluid passageway defining anopening at said proximal end and at said distal end portion; and afitting associated with said proximal end of said distraction member forfluidly connecting said distraction member to a source of the fluentmaterial.
 14. The device for injecting a fluent material into a discspace according to claim 13, further comprising an elongated cannuladefining a lumen therethrough, said cannula having a first fitting atone end thereof configured for fluid tight connection to said fitting ofsaid distraction member and a second fitting at an opposite end thereofconfigured for fluid connection to a source of the fluent material. 15.The device for injecting a fluent material into a disc space accordingto claim 14, wherein said distraction member is integral with saidcannula and said second fitting is said fitting associated with saidproximal end of said distraction member.
 16. The device for injecting afluent material into a disc space according to claim 13, wherein atleast said distal end portion of said distraction member isbullet-shaped.
 17. The device for injecting a fluent material into adisc space according to claim 13, wherein at least said distal endportion of said distraction member is wedge-shaped with oppositesubstantially flat sides.
 18. The device for injecting a fluent materialinto a disc space according to claim 13, wherein at least said distalend portion of said distraction member is cruciate-shaped.
 19. Thedevice for injecting a fluent material into a disc space according toclaim 13, wherein at least said distal end portion of said distractionmember is I-beam shaped.
 20. The device for injecting a fluent materialinto a disc space according to claim 13, wherein at least said distalend portion of said distraction member is C-shaped.
 21. The device forinjecting a fluent material into a disc space according to claim 13,wherein said fluid passageway defines a plurality of openings at saiddistal end portion of said distraction member.
 22. The device forinjecting a fluent material into a disc space according to claim 21,wherein: said fluid passageway is an elongated passageway extending fromsaid proximal end to said distal end portion of said distraction member;and said plurality of openings includes an opening along the length ofsaid elongated passageway and a plurality of openings transverse to saidelongated passageway.
 23. The device for injecting a fluent materialinto a disc space according to claim 13, wherein said distraction memberdefines a vent opening separate from said fluid passageway.
 24. Thedevice for injecting a fluent material into a disc space according toclaim 13, further comprising an injection tube sized to extend throughsaid fluid passageway in said distraction member, said injection tubehaving a proximal end configured for fluidly connecting to a source ofthe fluent material and a discharge opening at an opposite distal end,said distal end configured to be disposed within the disc space whenextending through said fluid passageway.
 25. The device for injecting afluent material into a disc space according to claim 24, furthercomprising a seal disposed between said passageway in said distractionmember and said injection tube.
 26. The device for injecting a fluentmaterial into a disc space according to claim 24, wherein said injectiontube is sized relative to said fluid passageway so that said distal endof said injection tube can be manipulated within the disc space whensaid injection tube extends through said fluid passageway.
 27. Thedevice for injecting a fluent material into a disc space according toclaim 24, wherein said distraction member defines a vent openingseparate from said fluid passageway.
 28. The device for injecting afluent material into a disc space according to claim 13, wherein saiddistraction member is formed of a bioresorbable material.
 29. The devicefor injecting a fluent material into a disc space according to claim 13,wherein said distraction member includes sealing element associated witha proximal portion of said distal end portion, said sealing elementconfigured to provide a substantially fluid-tight seal within the discspace.
 30. The device for injecting a fluent material into a disc spaceaccording to claim 29, wherein said sealing element includes a number ofseal rings disposed on said distal end portion.
 31. The device forinjecting a fluent material into a disc space according to claim 30,wherein said seal rings are integral with said distal end portion. 32.The device for injecting a fluent material into a disc space accordingto claim 31, wherein said seal rings are elastomeric rings mounted onsaid distal end portion.